1. Field of the Invention
The present invention relates to a core adapted for a choke and, more particularly, to a core having a pillar with a non-circular and non-rectangular cross section.
2. Background of the Invention
A choke is used for stabilizing a circuit current to achieve a noise filtering effect, and a function thereof is similar to that of a capacitor, by which stabilization of the current is adjusted by storing and releasing electrical energy of the circuit. Compared to the capacitor that stores the electrical energy by an electrical field (electric charge), the choke stores the same by a magnetic field.
In the past, the chokes are generally applied in electronic devices such as DC/DC converters and battery chargers, and applied in transmission devices such as modems, asymmetric digital subscriber lines (ADSL) or local area networks (LAN), etc. The chokes have also been widely applied to information technology products such as notebooks, mobile phones, LCD displays, and digital cameras, etc. Therefore, a height and size of the choke will be one the concerns due to the trend of minimizing the size and weight of the information technology products.
As shown in FIG. 1, the choke 1 disclosed in U.S. Pat. No. 7,209,022 includes a drum-core 10, a wire 12, an exterior resin 14, and a pair of external electrodes 16.
Furthermore, as shown in FIG. 2, the cross section of the pillar 100 of the drum-core 10 is circular. In general, the larger an area of the cross section of the pillar 100 is, the better the characteristics of the choke 1 are. However, since the shape of the cross section of the pillar 100 is circular and the winding space S has to be reserved for winding the wire 12, the area of the cross section of the pillar 100 is limited accordingly, so that saturation current cannot be raised effectively.
There is another drum-core with a rectangular pillar disclosed in U.S. Pat. No. 7,495,538 (hereinafter the '538 patent). In the '538 patent, since the shape of the cross section of the pillar is rectangular, the wire may be damaged at sharp corners of the pillar, and the characteristics of the choke (e.g., saturation current, direct current resistance, magnetic flux density, etc.) are worse.